when I upload or download something to server (debian8).
File size does not matter, mostly small files 1-50 MB.
I have this error since 2 weeks everyday (version 5.8.0 - now 5.8.1 beta)
Tried with my 3 vps servers and always the same.
I don´t know why, could it be that something changes on my servers and this is no winscp issue ?

Please attach a full log file showing the problem (using the latest version of WinSCP).

To generate log file, enable logging, log in to your server and do the operation and only the operation that causes the error. Submit the log with your post as an attachment. Note that passwords and passphrases not stored in the log. You may want to remove other data you consider sensitive though, such as host names, IP addresses, account names or file names (unless they are relevant to the problem). If you do not want to post the log publicly, you can mark the attachment as private.